Insensitive mutations and overexpressed detoxification genes in diamondback moth
We used FastD-TR to detect insensitive RyR mutations in two resistant populations, ZZ and CHR, and a sensitive population, CHS, of P. xylostella . The results showed that the frequencies of the insensitive mutation G4946E were 2.32%, 66.1% and 94.55% in CHS, ZZ and CHR, respectively (Table 1 ) (30 individuals in pool,one mutated allele can be detected in a pool containing 59 wild type alleles) . However, FastD-MR searching showed that no detoxification gene was expressed more than two-fold (|log2FoldChange| > 1, P-value < 0.01) higher in the CHR population. In contrast, six detoxification genes were overexpressed in the ZZ population (Table 2 ). Among these genes, CYP6a2 was overexpressed 10.82-fold in ZZ population. CYP6BG1 had elevated expression levels by 3.3-fold in the ZZ population. These genes were reported to confer chlorantraniliprole resistance (X. Li, Li, Zhu, Gao, & Liang, 2018). Our results indicated that both the insensitive RyR mutation G4946E and six overexpressed detoxification genes contribute to the resistance to chlorantraniliprole in P. xylostella populations.